The present invention relates to ovens and, more particularly, to ovens employing an impingement air flow method.
Examples of forced air or impingement ovens that use conveyors can be found in the prior art. A dual conveyor oven is disclosed by Smith in U. S. Pat. No. 4,474,498 where dual sets of air manifolds are utilized to provide heated air to two conveyors in an oven cabinet. An impeller arrangement is disclosed that draws return air from the front and exhausts re-heated air vertically into adjacent air manifolds. While effective, this arrangement does not provide a dual conveyor oven with a low profile nor does it provide for the easy and quick removal of the conveyors via a removable front panel. Furthermore, the conveyor speed cannot be individually controlled.
Another dual conveyor oven is disclosed by Wolfe in U. S. Pat. No. 5,832,812, which employs two, side-fed centrifugal fans mounted on a common shaft having an axis parallel to the direction of conveyor travel. This design has inherent problems in shaft vibration during operation due the shaft""s length and the fans are difficult to remove for service and cleaning. Furthermore, the style of centrifugal fan in this design creates an air flow pattern that is much more difficult to balance than alternative fan designs. This design also requires the oven to have a deep xe2x80x9cfootprintxe2x80x9d that is not always practical in restaurants. Finally, the burner tube design and location does not provide uniform return air re-heating before air enters the side-fed centrifugal fans along with difficult service and replacement of the burner tube, fans and fan housings.
A single conveyor, stackable conveyor oven is disclosed by Bruno in U. S. Pat. No. 5,277,105 that utilizes two, rear-fed, backward-inclined blade centrifugal fans. The ""105 patent discloses a front-mounted burner tube that is mounted perpendicular to the direction of conveyor travel. This burner tube orientation provides uneven and non-uniform heat patterns within the oven cabinet. No provision is made to remove the conveyors quickly and easily. The conveyor wire belt must be removed and the conveyor folded for removal. Each centrifugal fan is driven by an individual electric motor that increases service cost over the life of the unit. The front mounted oven controls disclosed in this patent require dedicated cooling fans to prevent damage from excessive heat build-up that again increase service costs. Finally, this design requires a deep xe2x80x9cfootprintxe2x80x9d that is not always practical in restaurants.
Finally, the stackable conveyor oven disclosed by Crisp in U.S. Pat. No. 5,025,775 utilizes two axial fans with separate motors mounted in the fan box to provide heated air movement. Only three ovens may be stacked to provide only three conveyor levels. As two motors are required per oven, service costs are increased over the unit""s service life. Furthermore, no quick and easy conveyor removal method is disclosed. Lastly, the controls are mounted on the side of the bake chamber. In a double or triple stack configuration, heat from the lower ovens rises and damages the sensitive electrical controls again increasing lifetime service costs.
While the prior art yields a number of conveyor oven designs having various axial and centrifugal fan air manifold arrangements, none of these teach the novel features and associated benefits found in the present invention.
The shortcomings inherent in the prior art are overcome by the present invention, which comprises a low profile, dual conveyor impingement oven having a bake chamber, two conveyor assemblies, a fan box with two centrifugal fans with axes mounted perpendicular to the direction of conveyor travel, two hot air distribution manifolds, six side-mounted, return air ducts and a drive end control unit. Other embodiments include a single conveyor oven with two centrifugal fans or a single conveyor oven with a shorter bake chamber that requires only a single centrifugal fan.
Each conveyor is positioned horizontally in the bake chamber to transport food products from one end to the other. Each conveyor has its own speed control to allow two separate bake times in a single oven. The bake chamber utilizes a cantilever design that allows easy and quick conveyor, air finger and return air duct removal from the front of the oven. When the front panel is removed, complete access is provided for cleaning or maintenance. The bake chamber is mounted to the fan box and may be removed if required for oven installation or maintenance.
The fan box contains two, backward-inclined blade, rear-fed centrifugal fans spaced along the length of the bake chamber. The rotational axis of each fan is perpendicular to the direction of conveyor travel. One electric motor mounted in the drive end provides power to both fans.
A burner tube is mounted at the rear of the fan box. The burner tube has openings to allow heated gas to exit the tube and heat the air being drawn into each fan. The design of the burner tube and the fact that each fan has only a single opening where heated air is drawn provides a much more uniform heat pattern when compared to the prior art.
Heated air is drawn into each fan""s inlet, which is operating at low pressure. Centrifugal force is imparted on the air and it is pressurized as it moves outward into each fan""s housing. The fan housing operates at a uniform, high pressure. The pressurized air is then directed into the three air fingers that are connected to the fan housing. The air fingers are adapted to distribute the heated air uniformly in the bake chamber on to food products being transported on either the top or bottom conveyor. This novel use of a backward-inclined blade centrifugal fan combined with a fan housing and three hot air fingers provides improved air flow that results in more uniform air distribution to the top and bottom of both conveyors and a uniform heat pattern within the bake chamber.
The bake chamber contains six return air ducts that channel spent cooking air back into the fan box for re-heating. These return air ducts greatly reduce the amount of spent air that escapes through the conveyor openings thereby increasing operating efficiency.
Appropriate control means are located in the drive end. These controls provide electricity to the main fan motor, the conveyor motors, the combustion air motor and control power to the temperature and conveyor time controls and the gas valves.
Due to the invention""s low-profile design, it is possible to stack two units and provide a total of four conveyor levels. Furthermore, the novel use of centrifugal fans whose axis of rotation is perpendicular to the direction of conveyor travel allows the ovens front to back dimension or depth to be minimized. Therefore, the present invention provides the maximum baking capacity in the smallest xe2x80x9cfootprint.xe2x80x9d In addition to maximizing cooking capacity, menu flexibility is also increased with the ability to cook on four separate conveyors with each operating at a separate speed.
Yet another advantage of the present invention is the ability to quickly and easily remove the conveyors, air fingers and return air ducts for cleaning or service. The removable front panel provides instant access to all components located inside the bake chamber. The side mounted oven controls are located away from the source of heat that will extend their service life. Since all oven controls and motors are located in the drive end, time required to replace any of these components is minimized.
These and other advantages of the present invention are provided below.